Purpose: In order to assess the severity of the primary diffuse brain injury, we propose a new grading system classified by the degree of the initial force expressed by presence or absence, and the duration of the loss of consciousness.

Grading system of the diffuse brain injury: It is divided into 4 grades as follows:

Grade I (no damage): no consciousness disturbance* immediately after injury.

Grade II (minor damage): transient consciousness disturbance or some duration of amnesia immediately after injury.

Grade III (moderate damage): consciousness disturbance immediately after injury, which recovers within 6 hrs.

Grade IV (severe damage): consciousness disturbance immediately after injury, which continues over 6 hrs.

Discussion and conclusion: Currently morphological diagnosis of the head injury is quite easy with the computed tomography, but the classification of the grade of the severity is not easy. There are several types of classification of the traumatic brain injury either using conventional terminologies, or based on the severity of conscious disturbance, or CT findings. It seems clear that the severity of the initial force is the primary factor which influences the clinical course after the head injury. Therefore, we propose a new grading system of the primary diffuse brain injury by means of the degree of the initial force assessed by the presence or absence, and the duration of the loss of consciousness. This new grading system could be used to evaluate the effectiveness of any kinds of treatments and predict the outcome at the early stage.